Pacific Trade Winds Delay Global Warming As They Pull Heat Into Ocean
Scientists have long wondered why the surface of the Pacific Ocean has been colder for the past 13 years. Now they are pretty close to the answer. Equatorial trade winds, which have taken on unprecedented strength, may be forcing heat deeper into the ocean.
According to a recent study, published in the journal Nature Climate Change, these trade winds have accelerated dramatically, causing the circulation in the Pacific. In turn, the winds are pulling more heat from the air, transferring it into the subsurface ocean, which results in cooler waters surging to the surface. "Scientists have long suspected that extra ocean heat uptake has slowed the rise of global average temperatures, but the mechanism behind the hiatus remained unclear," said Professor Matthew England, lead author of the study and a chief investigator at the ARC Centre of Excellence for Climate System Science, in a press release.
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The research, however, also found that the Pacific won't be holding the heat permanently. In due time, the trade wind strength will return to normal, causing heat to return to the atmosphere. "Our research suggests heat will quickly return to the atmosphere," England said in the release. "So global temperatures looks set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade."
The Pacific trade winds that began strengthening during the 1990s continue to this day, according to the researchers. In the past, climate models failed to see trade wind strengths of the magnitude observed in the current study, which also meant that they couldn't pick up on a hiatus in warming. But after the researchers added the trade winds to their model, the observations matched the global average temperatures.
"The winds lead to extra ocean heat uptake, which stalled warming of the atmosphere ... Unfortunately, however, when the hiatus ends, global warming looks set to be rapid," England said in the release. This will happen because the heat doesn't go very deep into the ocean, and "one the winds abate, heat is returned rapidly to the atmosphere."
Global average temperatures don't rise continuously, according to England. Instead, warming takes place in a series steps with steady temperatures in-between - as shown by the current surface warming hiatus. "We should be very clear," England said in the release. "The current hiatus offers no comfort - we are just seeing another pause in warming before the next inevitable rise in global temperatures."
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